Subtidal area only
Intertidal area only
Both intertidal area and subtidal areas
On the beach
Pentamerous
Porcupine
Dome
Toothpick
Echinoderms
Strongylocentrotus
Animalia
Purpuratus
Nose
Mouth
Spine
Feet
Because a sea urchin's egg is relatively big
Because sea urchins have large numbers of eggs
Because sea urchins have large numbers of relatively big eggs
Because the eggs make great omlettes
Sea cucumbers
Other sea urchins
Small fish
Algae